Technical Field
The present invention relates to an inorganic optical element including a birefringent film having a columnar structure, and a method for producing the inorganic optical element.
Background Art
Although a birefringent film having a columnar structure which is formed by obliquely vapor-depositing inorganic particles on a substrate surface has conventionally been used, there is concern that a phase difference varies depending on an amount of moisture contained in a void in the birefringent film. Therefore, for example, in the technologies described in PTLs 1 and 2, a protective film is formed on an obliquely vapor-deposited film to hold occluded water. In the technology described in PTL 3, a silane coupling agent containing a highly hydrophobic fluoroalkyl group is used to dispose a surface modification layer on a birefringent film, to thereby inhibit moisture from being adsorbed due to its water repellency.